A conventional method for transporting particulate or granular material through a dryer is on what is referred to as a pan conveyor. Each pan of the conveyor is provided with a perforated bottom, and air is caused to circulate within the dryer through said perforations and through the particulate material being conveyed in the pan conveyor.
A typical such pan conveyor is shown in prior U.S. Pat. No. 3,331,490 issued to Jeffrey Galion Manufacturing Company. A line of pans are arranged in succession carried by and between oppositely disposed chains, and the material being conveyed is carried within the pans. Individual pans are articulated with respect to each other so that the conveyor can bend around end driving sprockets and the like. The pans are provided with traveling sides or guards which are welded to the perforated bottom to contain the particulate material, and also to engage stationary baffle plates or gaurds within the dryer. Thus, the drying air is directed through the particulate material. Wear resistant seals are provided between the traveling guards and the stationary baffles to seal the air flow.
The sides of successive pans are not connected together, but are instead in sliding overlapping engagement because of the larger turning radius required for the sides around the end sprockets. One problem with this construction, and all pan conveyors, is the complexity and cost of the construction. In addition, the pan conveyors are heavy, requiring heavy-duty sprockets and other components. Further, their design obviously requires a large turning radius around the conveyor sprocket centers resulting in a bulky dryer construction.
Another known practice related to conveyor dryers is to use a metallic screen or perforated sheet metal conveyor as disclosed in prior U.S. Pat. No. 2,732,631, the drying being affected by the passage of hot air throgh and/or across the conveyor. In order to seal the flow of air across material on the conveyor, stationary wear resistant guards are provided extending between a dryer hood and the metallic screen.
It is known to provide in a baking oven a conveyor having a carrying run wherein the conveyor is a flat, flexible belt. The conveyor apparatus is provided with means for forming the belt into the shape of a trough. Such a construction is shown in prior U.S. Pat. No. 3,374,751. The conveyor flexible belt in this patent is impervious to the flow of air therethrough, and in fact, the conveyor assembly is provided with a horizontal bed or table beneath the conveyor flexible belt to support the same in its path of travel through the oven. Thus, even if the belt were pervious, this supporting plate would prevent the flow of air through the belt. Without the plate, the belt would be incapable of supporting relatively heavy loads.
Examples of other conveying apparatus comprising flexible belts and means to form the belts into troughs are shown in the following patents: British Pat. No. 661,027; Polish Pat. No. 47,517; U.S. Pat. No. 2,998,121; U.S. Pat. No. 3,381,799; U.S. Pat. No. 3,734,271; U.S. Pat. No. 3,627,111; and French Pat. No. 631,898.
The British Pat. No. 661,027 shows a conveyor belt which is supported by a plurality of spaced-apart slats, the belt being fastened to the slats with a plurality of rivets. The rivets are spaced inwardly from the sides of the belt allowing the belt sides to be turned up by guides to form a trough. The conveyor belt assembly of this patent would not be useful in a dryer for drying particulate material by the flow of drying air through the material since the belt shown in the patent is impervious to the flow of air.
Polish Pat. No. 47,517 appears to show a structure similar to that of the British patent. The conveyor belt of this patent also appears to be impervious to the flow of air through it.
U.S. Pat. No. 2,998,121 shows a guide arrangement in which a conveyor belt is supported by a plurality of spaced-apart rollers. Again, the belt shown is impervious to the flow of air through it and would not be suitable for the type of dryer to which the present invention is directed.
The remaining patents simply show a plurality of various guide mechanisms for forming a flexible belt into a trough.